Pain and activity limitation: Hip pain will be assessed by a horizontal visual analogue scale (VAS) (0-100 mm; 0 represents "no pain" and 100 represents "as much pain he/she can possibly imagine") (Revill et al. 1976). Both self-reported and observed functional capacity will be evaluated. Self-reported functional capacity will be registered by the disease-specific questionnaire Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) (Bellamy et al. 1988). Observed functional capacity will be assessed by the 6 minute walking test (Enright, 2003), where the patient is instructed to walk as quickly/fast as possible forth and back on a 20 m course, and by the subaximal bikecycle test (Astrand, 1986) where the heart-rate is registered on a constant load and speed.